分类: 农、林、牧、渔 >> 土壤学 提交时间: 2022-10-14 合作期刊: 《干旱区科学》
摘要:Litter and root activities may alter the temperature sensitivity (Q10) of soil respiration. However, existing studies have not provided a comprehensive understanding of the effects of litter and root carbon inputs on the Q10 of soil respiration in different seasons. In this study, we used the trench method under in situ conditions to measure the total soil respiration (Rtotal), litter-removed soil respiration (Rno-litter), root-removed soil respiration (Rno-root), and the decomposition of soil organic matter (i.e., both litter and root removal; RSOM) in different seasons of pioneer (Populus davidiana Dode) and climax (Quercus liaotungensis Mary) forests on the Loess Plateau, China. Soil temperature, soil moisture, litter biomass, fine root biomass, litter carbon, and root carbon were analyzed to obtain the drive mechanism of the Q10 of soil respiration in the two forests. The results showed that the Q10 of soil respiration exhibited seasonality, and the Q10 of soil respiration was higher in summer. The litter enhanced the Q10 of soil respiration considerably more than the root did. Soil temperature, soil moisture, fine root biomass, and litter carbon were the main factors used to predict the Q10 of different soil respiration components. These findings indicated that factors affecting the Q10 of soil respiration highly depended on soil temperature and soil moisture as well as related litter and root traits in the two forests, which can improve our understanding of soil carbon–climate feedback in global warming. The results of this study can provide reference for exploring soil respiration under temperate forest restoration.
分类: 地球科学 >> 地理学 提交时间: 2021-09-08 合作期刊: 《干旱区科学》
摘要: There are numerous valley farmlands on the Chinese Loess Plateau (CLP), where suffers from low soil quality and high risk of soil salinization due to the shallow groundwater table and poor drainage system. Currently, research on the evolution processes and mechanisms of soil quality and salinization in these dammed-valley farmlands on the CLP is still inadequately understood. In this study, three kinds of dammed-valley farmlands in the hilly-gully areas of the northern CLP were selected, and the status of soil quality and the impact factors of soil salinization were examined. The dammed-valley farmlands include the new farmland created by the project of Gully Land Consolidation, the 60-a farmland created by sedimentation from check dam, and the 400-a farmland created by sedimentation from an ancient landslide-dammed lake. Results showed that (1) the newly created farmland had the lowest soil quality in terms of soil bulk density, porosity, soil organic carbon and total nitrogen among the three kinds of dammed-valley farmlands; (2) soil salinization occurred in the middle and upper reaches of the new and 60-a valley farmlands, whereas no soil salinization was found in the 400-a valley farmland; and (3) soil salinization and low soil nutrient were determined to be the two important factors that impacted the soil quality of the valley farmlands in the hilly-gully mountain areas of the CLP. We conclude that the dammed-valley farmlands on the CLP have a high risk of soil salinization due to the shallow groundwater table, alkalinity of the loessial soil and local landform feature, thus resulting in the low soil quality of the valley farmlands. Therefore, strengthening drainage and decreasing groundwater table are extremely important to improve the soil quality of the valley farmlands and guarantee the sustainable development of the valley agriculture on the CLP.
分类: 地球科学 >> 地理学 提交时间: 2020-11-25 合作期刊: 《干旱区科学》
摘要: Amygdalus pedunculata Pall. is a major species that is widely planted in afforested soils with different textures in the transitional zone between Mu Us Desert and Loess Plateau, China. However, the responses of A. pedunculata to increasing intensity of water stress in different textural soils are not clear. Here, we conducted a soil column experiment to evaluate the effects of different textures (sandy and loamy) on water consumption, water use efficiency (WUE), biomass accumulation and ecological adaptability of A. pedunculata under increasing water stress, i.e., 90% (±5%) FC (field capacity), 75% (±5%) FC, 60% (±5%) FC, 45% (±5%) FC and 30% (±5%) FC in 2018. A. pedunculata grown in the sandy soil with the lowest (30% FC) and highest (90% FC) water contents had respectively 21.3%–37.0% and 4.4%–20.4% less transpiration than those with other water treatments (45%–75% FC). In contrast, A. pedunculata transpiration in the loamy soil decreased with decreasing water content. The magnitude of decrease in transpiration increased with increasing level of water deficit (45% and 30% FC). Mean daily and cumulative transpirations of the plant were significantly lower in the sandy soil than in the loamy soil under good water condition (90% FC), but the reverse was noted under water deficit treatments (45% and 30% FC). Plant height, stem diameter and total biomass initially increased with decreasing water content from 90% to 75% FC and then declined under severe water deficit conditions (45% and 30% FC) in the sandy soil. However, these plant parameters decreased with decreasing water content in the loamy soil. WUE in the sandy soil was 7.8%–12.3% higher than that in the loamy soil, which initially increased with decreasing water content from 90% to 75% FC and then declined under water deficit conditions (45% and 30% FC). The study showed that plant transpiration, biomass production and WUE responded differentially to increasing intensity of water stress in the sandy and loamy soils. The contrasting responses of A. pedunculata to water stress in different textural soils can guide future revegetation programs in the northern region of Chinese Loess Plateau by considering plant adaptability to varying soil and water conditions.
分类: 地球科学 >> 地球科学史 提交时间: 2018-10-29 合作期刊: 《干旱区科学》
摘要: Soil erosion on farmland is a critical environmental issue and the main source of sediment in the Yellow River, China. Thus, great efforts have been made to reduce runoff and soil loss by restoring vegetation on abandoned farmland. However, few studies have investigated runoff and soil loss from sloping farmland during crop growth season. The objective of this study was to investigate the effects of soil management on runoff and soil loss on sloping farmland during crop growth season. We tested different soybean growth stages (i.e., seedling stage (R1), initial blossoming stage (R2), full flowering stage (R3), pod bearing stage (R4), and initial filling stage (R5)) and soil management practice (one plot applied hoeing tillage (HT) before each rainfall event, whereas the other received no treatment (NH)) by applying simulated rainfall at an intensity of 80 mm/h. Results showed that runoff and soil loss both decreased and infiltration amount increased in successive soybean growth stages under both treatments. Compared with NH plot, there was less runoff and higher infiltration amount from HT plot. However, soil loss from HT plot was larger than that from NH plot in R1–R3, but lower in R4 and R5. In the early growth stages, hoeing tillage was effective for reducing runoff and enhancing rainfall infiltration. By contrast, hoeing tillage enhanced soil and water conservation during the late growth stages. The total soil loss from HT plot (509.0 g/m2) was 11.1% higher than that from NH plot (457.9 g/m2) in R1–R5. However, the infiltration amount from HT plot (313.9 mm) was 18.4% higher than that from NH plot (265.0 mm) and the total runoff volume from HT plot was 49.7% less than that from NH plot. These results indicated that crop vegetation can also act as a type of vegetation cover and play an important role on sloping farmland. Thus, adopting rational soil management in crop planting on sloping farmland can effectively reduce runoff and soil loss, as well as maximize rainwater infiltration during crop growth period.
分类: 地球科学 >> 地球科学史 提交时间: 2018-10-29 合作期刊: 《干旱区科学》
摘要: A large-scale afforestation project has been carried out since 1999 in the Loess Plateau of China. However, vegetation-induced changes in land surface temperature (LST) through the changing land surface energy balance have not been well documented. Using satellite measurements, this study quantified the contribution of vegetation restoration to the changes in summer LST and analyzed the effects of different vegetation restoration patterns on LST during both daytime and nighttime. The results show that the average daytime LST decreased by 4.3°C in the vegetation restoration area while the average nighttime LST increased by 1.4°C. The contributions of the vegetation restoration project to the changes in daytime LST and nighttime LST are 58% and 60%, respectively, which are far greater than the impact of climate change. The vegetation restoration pattern of cropland (CR) converting into artificial forest (AF) has a cooling effect during daytime and a warming effect at nighttime, while the conversion of CR to grassland has an opposite effect compared with the conversion of CR to AF. Our results indicate that increasing evapotranspiration caused by the vegetation restoration on the Loess Plateau is the controlling factor of daytime LST change, while the nighttime LST change is affected by soil humidity and air humidity.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2018-04-24 合作期刊: 《干旱区科学》
摘要: Knowledge about the effects of vegetation types on soil properties and on water dynamics in the soil profile is critical for revegetation strategies in water-scarce regions, especially the choice of vegetation type and human management measures. We focused on the analysis of the effects of vegetation type on soil hydrological properties and soil moisture variation in the 0–400 cm soil layer based on a long-term (2004―2016) experimental data in the northern Loess Plateau region, China. Soil bulk density (BD), saturated soil hydraulic conductivity (Ks), field capacity (FC) and soil organic carbon (SOC) in 2016, as well as the volumetric soil moisture content during 2004–2016, were measured in four vegetation types, i.e., shrubland (korshinsk peashrub), artificial grassland (alfalfa), fallow land and cropland (millet or potato). Compared with cropland, revegetation with peashrub and alfalfa significantly decreased BD and increased Ks, FC, and SOC in the 0–40 cm soil layer, and fallow land significantly increased FC and SOC in the 0–10 cm soil layer. Soil water storage (SWS) significantly declined in shrubland and grassland in the 40–400 cm soil layer, causing severe soil drought in the deep soil layers. The study suggested that converting cropland to grassland (alfalfa) and shrubland (peashrub) improved soil-hydrological properties, but worsened water conditions in the deep soil profile. However, natural restoration did not intensify deep-soil drying. The results imply that natural restoration could be better than revegetation with peashrub and alfalfa in terms of good soil hydrological processes in the semi-arid Loess Plateau region.
分类: 生物学 >> 植物学 >> 植物生态学和植物地理学 提交时间: 2025-03-18 合作期刊: 《干旱区科学》
摘要: Under current climate warming, the growth resilience of plantation forests after extreme droughts has garnered increasing attention. Platycladus orientalis Linn. is an evergreen tree species commonly used for afforestation, and the stability of P. orientalis plantation forests in the Loess Hilly region directly affects the ecological and environmental security of the entire Loess Plateau of China. However, systematic analyses of the growth resilience of P. orientalis plantation forests after extreme droughts along precipitation gradients remain scarce. In this study, we collected tree ring samples of P. orientalis along a precipitation gradient (255, 400, and 517 mm) from 2021 to 2023 and used dendroecological methods to explore the growth resilience of P. orientalis to drought stress on the Loess Plateau. Our findings revealed that the growth resilience of P. orientalis increased with increasing precipitation, enabling the trees to recover to the pre-drought growth levels. In regions with low precipitation (255 mm), the plantation forests were more sensitive to extreme droughts, struggling to recover to previous growth levels, necessitating conditional artificial irrigation. In regions with medium precipitation (400 mm), the growth of P. orientalis was significantly limited by drought stress and exhibited some recovery ability after extreme droughts, therefore warranting management through rainwater harvesting and conservation measures. Conversely, in regions with high precipitation (517 mm), the impacts of extreme droughts on P. orientalis plantation forests were relatively minor. This study underscored the need for targeted strategies tailored to different precipitation conditions rather than a "one-size-fits-all" approach to utilize precipitation resources effectively and maximize the ecological benefits of plantation forests. The findings will help maintain the stability of plantation forests and improve their ecosystem service functions in arid and semi-arid areas.
分类: 农、林、牧、渔 >> 土壤学 提交时间: 2024-12-17 合作期刊: 《干旱区科学》
摘要: The Chinese Loess Plateau has long been plagued by severe soil erosion and water scarcity. In this study, we proposed a technique involving the combined use of polymer SH and ryegrass and evaluated its effectiveness in modifying the water-holding characteristics of loess on the Chinese Loess Plateau (Chinese loess). We analysed the volumetric water content and water potential of untreated loess, treated loess with single polymer SH, treated loess with single ryegrass, and treated loess with both polymer SH and ryegrass using the loess samples collected from the Chinese Loess Plateau in July 2023. Moreover, fractal theory was used to analyse the fractal characteristics of the soil structure, and wet disintegration tests were conducted to assess the structural stability of both untreated and treated loess samples. The results showed that the loess samples treated with both polymer SH and ryegrass presented much higher volumetric water content and water potential than the untreated loess samples and those treated only with ryegrass or polymer SH. Moreover, the planting density of ryegrass affected the combined technique, since a relatively low planting density (20 g/m2) was conducive to enhancing the water-holding capacity of Chinese loess. The fractal dimension was directly correlated with both volumetric water content and water potential of Chinese loess. Specifically, since loess treated with both polymer SH and ryegrass was more saturated with moisture, its water potential increased, thus improving its water-holding capacity and fractal dimension. The combined technique better resisted disintegration than ryegrass alone but had slightly less resistance than polymer SH alone. This study provides insight into soil reinforcement and soil water management using polymetric materials and vegetation on the Chinese Loess Plateau.
分类: 农、林、牧、渔 >> 土壤学 提交时间: 2024-11-19 合作期刊: 《干旱区科学》
摘要: As one of typical areas in the world, northern Chinese Loess Plateau experiences serious wind-water erosion, which leads to widespread land degradation. During the past decades, an ecological engineering was implemented to reduce soil erosion and improve soil protection in this area. Thus, it is necessary to recognize the basic characteristics of soil protection for sustainable prevention and wind-water erosion control in the later stage. In this study, national wind erosion survey model and revised universal soil loss equation were used to analyze the spatiotemporal evolution and driving forces of soil protection in the wind-water erosion area of Chinese Loess Plateau during 2000–2020. Results revealed that: (1) during 2000–2020, total amount of soil protection reached up to 15.47×108 t, which was realized mainly through water and soil conservation, accounting for 63.20% of the total; (2) soil protection was improved, with increases in both soil protection amount and soil retention rate. The amounts of wind erosion reduction showed a decrease trend, whereas the retention rate of wind erosion reduction showed an increase trend. Both water erosion reduction amount and retention rate showed increasing trends; and (3) the combined effects of climate change and human activities were responsible for the improvement of soil protection in the wind-water erosion area of Chinese Loess Plateau. The findings revealed the spatiotemporal patterns and driving forces of soil protection, and proposed strategies for future soil protection planning in Chinese Loess Plateau, which might provide valuable references for soil erosion control in other wind-water erosion areas of the world.
分类: 农、林、牧、渔 >> 土壤学 提交时间: 2024-11-19 合作期刊: 《干旱区科学》
摘要: As one of typical areas in the world, northern Chinese Loess Plateau experiences serious wind-water erosion, which leads to widespread land degradation. During the past decades, an ecological engineering was implemented to reduce soil erosion and improve soil protection in this area. Thus, it is necessary to recognize the basic characteristics of soil protection for sustainable prevention and wind-water erosion control in the later stage. In this study, national wind erosion survey model and revised universal soil loss equation were used to analyze the spatiotemporal evolution and driving forces of soil protection in the wind-water erosion area of Chinese Loess Plateau during 2000–2020. Results revealed that: (1) during 2000–2020, total amount of soil protection reached up to 15.47×108 t, which was realized mainly through water and soil conservation, accounting for 63.20% of the total; (2) soil protection was improved, with increases in both soil protection amount and soil retention rate. The amounts of wind erosion reduction showed a decrease trend, whereas the retention rate of wind erosion reduction showed an increase trend. Both water erosion reduction amount and retention rate showed increasing trends; and (3) the combined effects of climate change and human activities were responsible for the improvement of soil protection in the wind-water erosion area of Chinese Loess Plateau. The findings revealed the spatiotemporal patterns and driving forces of soil protection, and proposed strategies for future soil protection planning in Chinese Loess Plateau, which might provide valuable references for soil erosion control in other wind-water erosion areas of the world.
分类: 地球科学 >> 地理学 提交时间: 2023-02-07 合作期刊: 《干旱区科学》
摘要: Check dams are widely used on the Loess Plateau in China to control soil and water losses, develop agricultural land, and improve watershed ecology. Detailed information on the number and spatial distribution of check dams is critical for quantitatively evaluating hydrological and ecological effects and planning the construction of new dams. Thus, this study developed a check dam detection framework for broad areas from high-resolution remote sensing images using an ensemble approach of deep learning and geospatial analysis. First, we made a sample dataset of check dams using GaoFen-2 (GF-2) and Google Earth images. Next, we evaluated five popular deep-learning-based object detectors, including Faster R-CNN, You Only Look Once (version 3) (YOLOv3), Cascade R-CNN, YOLOX, and VarifocalNet (VFNet), to identify the best one for check dam detection. Finally, we analyzed the location characteristics of the check dams and used geographical constraints to optimize the detection results. Precision, recall, average precision at intersection over union (IoU) threshold of 0.50 (AP50), IoU threshold of 0.75 (AP75), and average value for 10 IoU thresholds ranging from 0.500.95 with a 0.05 step (AP5095), and inference time were used to evaluate model performance. All the five deep learning networks could identify check dams quickly and accurately, with AP5095, AP50, and AP75 values higher than 60.0%, 90.0%, and 70.0%, respectively, except for YOLOv3. The VFNet had the best performance, followed by YOLOX. The proposed framework was tested in the Yanhe River Basin and yielded promising results, with a recall rate of 87.0% for 521 check dams. Furthermore, the geographic analysis deleted about 50% of the false detection boxes, increasing the identification accuracy of check dams from 78.6% to 87.6%. Simultaneously, this framework recognized 568 recently constructed check dams and small check dams not recorded in the known check dam survey datasets. The extraction results will support efficient watershed management and guide future studies on soil erosion in the Loess Plateau.
分类: 地球科学 >> 地球科学史 提交时间: 2020-10-20 合作期刊: 《干旱区科学》
摘要: Soil water is a critical resource, and as such is the focus of considerable physical research. Characterization of the distribution and spatial variability of soil water content (SWC) offers important agronomic and environmental information. Estimation of non-stationary and non-linear SWC distribution at different scales is a research challenge. Based on this context, we performed a case study on the Chinese Loess Plateau, with objectives of investigating spatial variability of SWC and soil properties (i.e., soil particle composition, organic matter and bulk density), and determining multi-scale correlations between SWC and soil properties. A total of 86 in situ sampling sites were selected and 516 soil samples (0–60 cm depth with an interval of 10 cm) were collected in May and June of 2019 along the Yangling-Wugong-Qianxian transect, with a length of 25.5 km, in a typical wheat-corn rotation region of the Chinese Loess Plateau. Classical statistics and empirical mode decomposition (EMD) method were applied to evaluate characteristics of the overall and scale-specific spatial variation of SWC, and to explore scale-specific correlations between SWC and soil properties. Results showed that the spatial variability of SWC along the Yangling-Wugong-Qianxian transect was medium to weak, with a variability coefficient range of 0.06–0.18, and it was gradually decreased as scale increased. We categorized the overall SWC for each soil layer under an intrinsic mode function (IMF) number based on the scale of occurrence, and found that the component IMF1 exhibited the largest contribution rates of 36.45%–56.70%. Additionally, by using EMD method, we categorized the general variation of SWC under different numbers of IMFs according to occurrence scale, and the results showed that the calculated scales among SWC for each soil layer increased in correspondence with higher IMF numbers. Approximately 78.00% of the total variance of SWC was extracted in IMF1 and IMF2. Generally, soil texture was the dominant control on SWC, and the influence of the three types of soil properties (soil particle composition, organic matter and bulk density) was more prominent at larger scales along the sampling transect. The influential factors of soil water spatial distribution can be identified and ranked on the basis of the decomposed signal from the current approach, thereby providing critical information for other researchers and natural resource managers.
分类: 地球科学 >> 地理学 提交时间: 2019-08-30 合作期刊: 《干旱区科学》
摘要: Soil tillage and straw retention in dryland areas may affect the soil aggregates and the distribution of total organic carbon. The aims of this study were to establish how different tillage and straw retention practices affect the soil aggregates and soil organic carbon (SOC) and total nitrogen (TN) contents in the aggregate fractions based on a long-term (approximately 15 years) field experiment in the semi-arid western Loess Plateau, northwestern China. The experiment included four soil treatments, i.e., conventional tillage with straw removed (T), conventional tillage with straw incorporated (TS), no tillage with straw removed (NT) and no tillage with straw retention (NTS), which were arranged in a complete randomized block design. The wet-sieving method was used to separate four size fractions of aggregates, namely, large macroaggregates (LA, >2000 μm), small macroaggregates (SA, 250–2000 μm), microaggregates (MA, 53–250 μm), and silt and clay (SC, <53 μm). Compared to the conventional tillage practices (including T and TS treatments), the percentages of the macroaggregate fractions (LA and SA) under the conservation tillage practices (including NT and NTS treatments) were increased by 41.2%–56.6%, with the NTS treatment having the greatest effect. For soil layers of 0–5, 5–10 and 10–30 cm, values of the mean weight diameter (MWD) under the TS and NTS treatments were 10.68%, 13.83% and 17.65%, respectively. They were 18.45%, 19.15% and 14.12% higher than those under the T treatment, respectively. The maximum contents of the aggregate-associated SOC and TN were detected in the SA fraction, with the greatest effect being observed for the NTS treatment. The SOC and TN contents were significantly higher under the NTS and TS treatments than under the T treatment. Also, the increases in SOC and TN levels were much higher in the straw-retention plots than in the straw-removed plots. The macroaggregates (including LA and SA fractions) were the major pools for SOC and TN, regardless of tillage practices, storing 3.25–6.81 g C/kg soil and 0.34–0.62 g N/kg soil. Based on the above results, we recommend the NTS treatment as the best option to boost soil aggregates and to reinforce carbon and nitrogen sequestration in soils in the semi-arid western Loess Plateau of northwestern China.
分类: 地球科学 >> 地理学 提交时间: 2019-06-20 合作期刊: 《干旱区科学》
摘要: Jujube (Ziziphus jujube Mill.) is a traditional economic forest crop and is widely cultivated in hilly areas of the Loess Plateau, China. However, soil desiccation was discovered in jujube plantations. Pruning is recognized as a water-saving method that can reduces soil water consumption. In this study, we monitored the jujube plots with control (CK), light (C1), medium (C2) and high (C3) pruning intensities during the jujube growing period of 2012–2015 to explore the effect of pruning intensity on soil moisture and water use efficiency (WUE) of jujube plantations in the hilly Loess Plateau Region. The results showed that pruning is an effective method for soil water conservation in jujube plantations. Soil moisture increased with increasing pruning intensity during the jujube growing period of 2012–2015. C1, C2 and C3 pruning intensities increased soil water storage by 6.1–18.3, 14.4–40.0 and 24.3–63.3 mm, respectively, compared to CK pruning intensity. Pruning promoted soil moisture infiltration to deeper soil layer. Soil moisture infiltrated to soil depths of 240, 280 and >300 cm under C3 pruning intensity, 220, 260 and 260 cm under C2 pruning intensity, 200, 240 and 220 cm under C1 pruning intensity, and 180, 200 and 160 cm under CK pruning intensity in 2013, 2014 and 2015, respectively. Soil water deficit was alleviated by higher pruning intensity. In 2013–2015, soil water change was positive under C2 (6.4 mm) and C3 (26.8 mm) pruning intensities but negative under C1 (–20.5 mm) and CK (–40.6 mm) pruning intensities. Moreover, pruning significantly improved fresh fruit yield and WUE of jujube plants. Fresh fruit yields were highest under C1 pruning intensity with the values of 6897.1–13,059.3 kg/hm2, which were 2758.4–4712.8, 385.7–1432.1 and 802.8–2331.5 kg/hm2 higher than those under CK, C2, and C3 pruning intensities during the jujube growing period of 2012–2015, respectively. However, C3 pruning intensity had the highest WUE values of 2.92–3.13 kg/m3, which were 1.6–2.0, 1.1–1.2 and 1.0–1.1 times greater than those under CK, C1 and C2 pruning intensities, respectively. Therefore, C3 pruning intensity is recommended to jujube plantations for its economic and ecological benefits. These results provide an alternative strategy to mitigate soil desiccation in jujube plantations in the hilly Loess Plateau Region, which is critical for sustainable cultivation of economic forest trees in this region.
分类: 地球科学 >> 地球科学史 提交时间: 2018-09-18 合作期刊: 《干旱区科学》
摘要: High and efficient use of limited rainwater resources is of crucial importance for the crop production in arid and semi-arid areas. To investigate the effects of different soil and crop management practices (i.e., mulching mode treatments: flat cultivation with non-mulching, flat cultivation with straw mulching, plastic-covered ridge with bare furrow and plastic-covered ridge with straw-covered furrow; and planting density treatments: low planting density of 45,000 plants/hm2, medium planting density of 67,500 plants/hm2 and high planting density of 90,000 plants/hm2) on rainfall partitioning by dryland maize canopy, especially the resulted net rainfall input beneath the maize canopy, we measured the gross rainfall, throughfall and stemflow at different growth stages of dryland maize in 2015 and 2016 on the Loess Plateau of China. The canopy interception loss was estimated by the water balance method. Soil water storage, leaf area index, grain yield (as well as it components) and water use efficiency of dryland maize were measured or calculated. Results showed that the cumulative throughfall, cumulative stemflow and cumulative canopy interception loss during the whole growing season accounted for 42.3%–77.5%, 15.1%–36.3% and 7.4%–21.4% of the total gross rainfall under different treatments, respectively. Soil mulching could promote the growth and development of dryland maize and enhance the capability of stemflow production and canopy interception loss, thereby increasing the relative stemflow and relative canopy interception loss and reducing the relative throughfall. The relative stemflow and relative canopy interception loss generally increased with increasing planting density, while the relative throughfall decreased with increasing planting density. During the two experimental years, mulching mode had no significant influence on net rainfall due to the compensation between throughfall and stemflow, whereas planting density significantly affected net rainfall. The highest grain yield and water use efficiency of dryland maize were obtained under the combination of medium planting density of 67,500 plants/hm2 and mulching mode of plastic-covered ridge with straw-covered furrow. Soil mulching can reduce soil evaporation and retain more soil water for dryland maize without reducing the net rainfall input beneath the maize canopy, which may alleviate the contradiction between high soil water consumption and insufficient rainfall input of the soil. In conclusion, the application of medium planting density (67,500 plants/hm2) under plastic-covered ridge with bare furrow is recommended for increasing dryland maize production on the Loess Plateau of China.
分类: 地球科学 >> 地球科学史 提交时间: 2018-09-18 合作期刊: 《干旱区科学》
摘要: Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies have examined the effects of vegetation restoration on soil properties and erodibility of gully head in the gully regions of the Loess Plateau. The objectives of this study were to quantify the effects of vegetation restoration on soil properties and erodibility in this region. Specifically, a control site in a slope cropland and 9 sites in 3 restored land-use types (5 sites in grassland, 3 in woodland and 1 in shrubland) in the Nanxiaohegou watershed of a typical gully region on the Loess Plateau were selected, and soil and root samples were collected to assess soil properties and root characteristics. Soil erodibility factor was calculated by the Erosion Productivity Impact Calculator method. Our results revealed that vegetation restoration increased soil sand content, soil saturated hydraulic conductivity, organic matter content and mean weight diameter of water-stable aggregate but decreased soil silt and clay contents and soil disintegration rate. A significant difference in soil erodibility was observed among different vegetation restoration patterns or land-use types. Compared with cropland, soil erodibility decreased in the restored lands by 3.99% to 21.43%. The restoration patterns of Cleistogenes caespitosa K. and Artemisia sacrorum L. in the grassland showed the lowest soil erodibility and can be considered as the optimal vegetation restoration pattern for improving soil anti-erodibility of the gully heads. Additionally, the negative linear change in soil erodibility for grassland with restoration time was faster than those of woodland and shrubland. Soil erodibility was significantly correlated with soil particle size distribution, soil disintegration rate, soil saturated hydraulic conductivity, water-stable aggregate stability, organic matter content and root characteristics (including root average diameter, root length density, root surface density and root biomass density), but it showed no association with soil bulk density and soil total porosity. These findings indicate that although vegetation destruction is a short-term process, returning the soil erodibility of cropland to the level of grassland, woodland and shrubland is a long-term process (8–50 years).
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2018-05-18 合作期刊: 《干旱区科学》
摘要: Understanding solute transport behaviors of deep soil profile in the Loess Plateau is helpful for ecological construction and agricultural production improvement. In this study, solute transport processes of a deep soil profile were measured by a conservative tracer experiment using 25 undisturbed soil cores (20 cm long and 7 cm diameter for each) continuously sampled from the surface downward to the depth of 500 cm in the Loess Plateau of China. The solute transport breakthrough curves (BTCs) were analyzed in terms of the convection-dispersion equation (CDE) and the mobile-immobile model (MIM). Average pore-water velocity and dispersion coefficient (or effective dispersion coefficient) were calculated using the CDE and MIM. Basic soil properties and water infiltration parameters were also determined to explore their influence on the solute transport parameters. Both pore-water velocity and dispersion coefficient (or effective dispersion coefficient) generally decreased with increasing depth, and the dispersivity fluctuated along the soil profile. There was a good linear correlation between log-transformed pore-water velocity and dispersion coefficient, with a slope of about 1.0 and an average dispersivity of 0.25 for the entire soil profile. Generally speaking, the soil was more homogeneous along the soil profile. Our results also show that hydrodynamic dispersion is the dominant mechanism of solute transport of loess soils in the study area.
分类: 地球科学 >> 大气科学 提交时间: 2024-12-17 合作期刊: 《干旱区科学》
摘要: Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems, and accurate evapotranspiration modeling is of great significance for hydrological, ecological, agricultural, and water resource management. Artificial forests are an important means of vegetation restoration in the western Loess Plateau, and accurate estimates of their evapotranspiration are essential to the management and development of water use strategies for artificial forests. This study estimated the soil moisture and evapotranspiration based on the HYDRUS-1D model for the artificial Platycladus orientalis (L.) Franco forest in western mountains of Loess Plateau, China from 20 April to 31 October, 2023. Moreover, the influence factors were identified by combining the correlation coefficient method and the principal component analysis (PCA) method. The results showed that HYDRUS-1D model had strong applicability in portraying hydrological processes in this area and revealed soil water surplus from 20 April to 31 October, 2023. The soil water accumulation was 49.64 mm; the potential evapotranspiration (ETp) was 809.67 mm, which was divided into potential evaporation (Ep; 95.07 mm) and potential transpiration (Tp; 714.60 mm); and the actual evapotranspiration (ETa) was 580.27 mm, which was divided into actual evaporation (Ea; 68.27 mm) and actual transpiration (Ta; 512.00 mm). From April to October 2023, the ETp, Ep, Tp, ETa, Ea, and Ta first increased and then decreased on both monthly and daily scales, exhibiting a single-peak type trend. The average ratio of Ta/ETa was 0.88, signifying that evapotranspiration mainly stemmed from transpiration in this area. The ratio of ETa/ETp was 0.72, indicating that this artificial forest suffered from obvious drought stress. The ETp was significantly positively correlated with ETa, and the R2 values on the monthly and daily scales were 0.9696 and 0.9635 (P<0.05), respectively. Furthermore, ETa was significantly positively correlated with temperature, solar radiation, and wind speed, and negatively correlated with relative humidity and precipitation (P<0.05); and temperature exhibited the highest correlation with ETa. Thus, ETp and temperature were the decisive contributors to ETa in this area. The findings provide an effective method for simulating regional evapotranspiration and theoretical reference for water management of artificial forests, and deepen understanding of effects of each influence factors on ETa in arid areas.
分类: 生物学 >> 生态学 提交时间: 2024-08-14 合作期刊: 《干旱区科学》
摘要: Soil erosion caused by unsustainable grazing is a major driver of grassland ecosystem degradation in many semi-arid hilly areas in China. Thus, grazing exclusion is considered as an effective method for solving this issue in such areas. However, some ecological and economic problems, such as slow grassland rejuvenation and limited economic conditions, have become obstacles for the sustainable utilization of grassland ecosystem. Accordingly, we hypothesized that the conflict between grassland use and soil conservation may be balanced by a reasonable grazing intensity. In this study, a two-year grazing fence experiment with five grazing intensity gradients was conducted in a typical grassland of the Loess Plateau in China to evaluate the responses of vegetation characteristics and soil and water losses to grazing intensity. The five grazing intensity gradients were 2.2, 3.0, 4.2, 6.7, and 16.7 goats/hm2, which were represented by G1–G5, respectively, and no grazing was used as control. The results showed that a reasonable grazing intensity was conducive to the sustainable utilization of grassland resources. Vegetation biomass under G1–G4 grazing intensity significantly increased by 51.9%, 42.1%, 36.9%, and 36.7%, respectively, compared with control. In addition, vegetation coverage increased by 19.6% under G1 grazing intensity. Species diversity showed a single peak trend with increasing grazing intensity. The Shannon-Wiener diversity index under G1–G4 grazing intensities significantly increased by 22.8%, 22.5%, 13.3%, and 8.3%, respectively, compared with control. Furthermore, grazing increased the risk of soil erosion. Compared with control, runoff yields under G1–G5 grazing intensities increased by 1.4, 2.6, 2.8, 4.3, and 3.9 times, respectively, and sediment yields under G1–G5 grazing intensities were 3.0, 13.0, 20.8, 34.3, and 37.7 times greater, respectively, than those under control. This result was mainly attributed to a visible decrease in litter biomass after grazing, which decreased by 50.5%, 72.6%, 79.0%, 80.0%, and 76.9%, respectively, under G1–G5 grazing intensities. By weighing the grassland productivity and soil conservation function, we found that both two aims were achieved at a low grazing intensity of less than 3.5 goats/hm2. Therefore, it is recommended that grassland should be moderately utilized with grazing intensity below 3.5 goats/hm2 in semi-arid hilly areas to achieve the dual goals of ecological and economic benefits. The results provide a scientific basis for grassland utilization and health management in semi-arid hilly areas from the perspective of determining reasonable grazing intensity to maintain both grassland production and soil conservation functions.
分类: 地球科学 >> 地理学 提交时间: 2022-01-30 合作期刊: 《干旱区科学》
摘要: Groundwater plays a dominant role in the eco-environmental protection of arid and semi-arid regions. Understanding the sources and mechanisms of groundwater recharge, the interactions between groundwater and surface water and the hydrogeochemical evolution and transport processes of groundwater in the Longdong Loess Basin, Northwest China, is of importance for water resources management in this ecologically sensitive area. In this study, 71 groundwater samples (mainly distributed at the Dongzhi Tableland and along the Malian River) and 8 surface water samples from the Malian River were collected, and analysis of the aquifer system and hydrological conditions, together with hydrogeochemical and isotopic techniques were used to investigate groundwater sources, residence time and their associated recharge processes. Results show that the middle and lower reaches of the Malian River receive water mainly from groundwater discharge on both sides of valley, while the source of the Malian River mainly comes from local precipitation. Groundwater of the Dongzhi Tableland is of a HCO3CaNa type with low salinity. The reverse hydrogeochemical simulation suggests that the dissolution of carbonate minerals and cation exchange between Ca2+, Mg2+ and Na+ are the main water-rock interactions in the groundwater system of the Dongzhi Tableland. The 18O (from 11.70 to 8.52) and 2H (from 86.15 to 65.75) values of groundwater are lower than the annual weighted average value of precipitation but closer to summer-autumn precipitation and soil water in the unsaturated zone, suggesting that possible recharge comes from the summer-autumn monsoonal heavy precipitation in the recent past (220 a). The corrected 14C ages of groundwater range from 3,000 to 25,000 a old, indicating that groundwater was mainly from precipitation during the humid and cold Late Pleistocene and Holocene periods. Groundwater flows deeper from the groundwater table and from the center to the east, south and west of the Dongzhi Tableland with estimated migration rate of 1.291.43 m/a. The oldest groundwater in the Quaternary Loess Aquifer in the Dongzhi Tableland is approximately 32,000 a old with poor renewability. Based on the 18O temperature indicator of groundwater, we speculate that temperature of the Last Glacial Maximum in the Longdong Loess Basin was 2.4C6.0C colder than the present. The results could provide us the valuable information on groundwater recharge and evolution under thick loess layer, which would be significative for the scientific water resources management in semi-arid regions.